Heat-recoverable articles such as heat-shrinkable tubes are used for, for example, protection, insulation, waterproofing, and corrosion protection of connected portions between insulated electrical wires, wiring terminals, metal tubes, and the like and for packaging of commercial products. For example, when a connected portion between insulated electrical wires is covered with a heat-shrinkable tube and heating is performed, the heat-shrinkable tube shrinks so as to conform to the shape of the connected portion and comes into close contact with the connected portion. Thus, the heat-shrinkable tube can protect the connected portion. From the viewpoint of manufacturability and usability, crosslinked polymers can be used for the heat-recoverable articles.
An olefin-based polymer having a gel fraction in a range of 20% to 80% has been proposed as an example of the crosslinked polymers (refer to Japanese Unexamined Patent Application Publication No. 2004-342868). Furthermore, a polymer having a degree of crosslinking of 25% or more has been proposed (refer to Japanese Unexamined Patent Application Publication No. 2007-172967).